Extended Forecast Discussion NWS Weather Prediction Center College Park MD 249 PM EDT Sat Jul 03 2021 Valid 12Z Tue Jul 06 2021 - 12Z Sat Jul 10 2021 ...Elsa is forecast to impact Florida and the Southeast through the middle of next week with heavy rainfall and potential for high winds... ...Repeating heavy rain is likely to persist over southern Texas through much of next week as low pressure lingers... ...Overview... In a fairly typical summer pattern, expect a strengthening upper ridge to prevail over the Great Basin/Desert Southwest while varying degrees of mean troughing align over the east-central U.S. A leading shortwave crossing the northeast quadrant of the lower 48 will push along a wavy cold front during most of next week. A trailing Pacific shortwave rounding the upper ridge should amplify into the Midwest/western Great Lakes toward the end of the week, supporting another area of low pressure and associated frontal system. The primary features of interest at lower latitudes will be Tropical Storm Elsa which should impact Florida and parts of the Southeast through the middle of next week, and a slow-moving upper trough/low that could produce heavy rainfall as it slowly drifts over Texas and into northern Mexico. ...Guidance/Predictability Evaluation... Overall a 00Z/06Z model blend transitioning to a model/ensemble mean blend provided a good starting point to reflect the most common themes of guidance while downplaying details that have lower confidence/predictability. For Elsa, the 06Z GFS provided the best template relative to latest National Hurricane Center advisories valid Tuesday-Thursday. ECMWF/UKMET runs are somewhat slower while the CMC is holding onto its recent typical fast bias. Over the past day or so the ECMWF has trended considerably toward the GFS for track while the GFS has trended weaker. Meanwhile there is good agreement in principle for the shortwave crossing the northeastern quadrant of the lower 48 and a second shortwave amplifying into the Midwest after rounding the western upper ridge. In both cases but especially for the latter, there are detail differences that have a meaningful effect on the surface evolution--but low predictability 5-7 days out in time. The blend approach reflects the most agreeable aspects of synoptic evolution while awaiting better clustering for specifics. ...Weather Highlights/Hazards... An upper low/trough drifting southwest over southern Texas into northern Mexico through next week will support a repeating heavy rain threat over that region most days, with multi-inch totals expected and localized five-day totals over a foot likely (though the heaviest looks to be just south of the Rio Grande). Farther northwest, late-day monsoonal type showers and thunderstorms are likely to continue through Wednesday over the Central/Southern Rockies. Any activity thereafter should be much lighter and more scattered. Around midweek Elsa will bring the potential for heavy rainfall, flooding, and high winds to parts of Florida and areas northeastward over the Southeast and southern Mid-Atlantic. Though somewhat less dramatic than in previous days, considerable spread still exists for Elsa's strength/track/timing along with associated effects. Monitor products from the National Hurricane Center for the latest information regarding Elsa. The wavy front pushing east from the Midwest/Great Lakes will produce periods of rain that could be locally moderate/heavy. After midweek the tropical moisture from Elsa could increase rain totals in the Mid-Atlantic/Northeast depending on Elsa's track/strength and any frontal interaction. The system forecast to reach the Midwest/Great Lakes toward the end of the week may be accompanied by meaningful rainfall as well. Expect the heat wave over a significant portion of the West to continue through next week as the Great Basin/Southwest upper ridge restrengthens. The Northwest and northern Great Basin should see highs 10-15F above normal most days with locally higher readings possible early and late in the period. For a brief time around Wednesday-Thursday some locations may be a little less above normal as a Pacific shortwave rounding the upper ridge brings a weak cold front through. Some daily records for highs/warm lows will be possible ahead of this weak front, while such potential could also be worth monitoring as the upper ridge rebounds late in the week. The southern High Plains/Texas will likely see highs 5-12F below average for most of the week due to cloudiness and rain from the persistent upper level disturbance there. Rausch/Jackson Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indices are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml